Each vertebra in the human spine has two sets of joints which interact with adjacent upper and lower joints. These joints are known as the facet joints, and are otherwise known as the zygapophyseal or apophyseal joints. Two joints are formed on each lateral side of the vertebra. The superior articular facet faces upward and the inferior articular facet faces downward, such that the superior articular facet of a lower vertebrae abuts the inferior articular facet of an adjacent upper vertebrae. The facet joints are located on the posterior of the spine adjacent the pedicle, lamina, and transverse process. The facet joints generally are hinge-like and allow limited flexion, extension, and twisting motion, while preventing excessive motion which could damage the spinal chord.
Various spinal reconstructive or treatment procedures require the removal of the facet joint and ligament structures. The joint and ligament must then be reconstructed artificially. Known artificial facet joints fail to provide the rigidity that is necessary to support the spine while permitting the flexibility to reassemble the facet joint.